I'm sure there are a few, but this is something I've never really thought about. My advice may not be the best, or it may not even be advice. It's just something I figured out from experience.

I've never been in that situation so I can't answer specifically, but I want to describe some of the ways I've thought about this topic, and the various reasons people may have to feel pressured to reciprocate. In particular, people tend to say "no, thanks" if someone says "no, thanks" too quickly, even if they think they didn't mean it. Here are some examples.

Saying "thanks" or "no thanks" too quickly when talking about something non-romantic is seen as "putting them on the spot" or something similar. I've been told this is a bad habit and it makes people uncomfortable (and there are people who say they try to avoid it). So in the case of "what should I do?" kind of situations, saying "I don't know" (rather than "no thanks" or "thank you, but I'd rather not" or some other formulaic "I don't know what you want so I'll just ignore the question") is seen as a much more gentle way to say "I don't want to date you right now."

"No thanks" can have a negative connotation if it's framed as rejection, which can happen if you say it to someone out of the blue and not really expecting them to reject. E.g. someone may be trying to decide if they want to go to a party you're hosting, and ask you "do you have any plans for X?" and you say "oh, I'm gonna do Y!" and they say "I'm not sure I want to go to the party, I don't want to put you out like this." They don't want to "put you out," they just want a polite way to say "no thanks." But then they go to the party (which they otherwise would have wanted to go to), and they find out the party has awful music, they sit down by a fire and they eat too many peanuts, there's a lot of "how are you doing?" going around and they don't really enjoy the party, and they just find the whole situation "awful, thanks a lot, I'm glad it's over." Then they text you in a few weeks "I'm sorry I really wasn't in the mood, I thought the party was fine but it really wasn't." You ask why they didn't tell you to not go, and they say "I just wanted to get a sense of how you felt about whether it would be a good thing to do." People do not enjoy being put in that position: they want to do what makes you happy, but they think they're putting you in an awkward and uncomfortable situation if they ask what that is and don't expect you to answer, because that might hurt their feelings.

"I'd rather not" can also be seen as "no thanks." So someone might not want to spend a whole weekend or more with you. They might feel like they don't have much in common – one person likes a certain movie, the other person does not, and the person who doesn't wants to talk about the movie, and the person who does not want to sit in silence for half an hour with a conversation that's just getting more and more awkward. So they say "I'd rather not" rather than "no thanks." This might be because they don't want to spend time with you or with other people who are just as bad as you (or you just aren't good at socializing in that way) but it's also possible that this might be coming from a place of self-protection – you're a nice person who doesn't ask for anything in return, so if you're not going to ask for anything, how are they supposed to know whether to ask for something?

Anyway, these are just some things I've thought about. In particular, I've learned that saying "no thanks" really does sound better than saying "no thanks," but a lot of people will still take it in the wrong way. Maybe what we need is an easy way to signal "I don't care if you want to have sex with me or not, so long as it isn't bothering you. My feeling on that has nothing to do with whether you want it." But that's not really feasible as a signal.

For reference, the context in which I have used "no thanks" is in non-sexual contexts, where people are asking if I want to join them for this or that social thing (a sports game, a movie, a date, a party, and so forth), which is not a situation where someone can know my heart. (Or where they should know my heart. Or where there is a presumption that anyone's heart matters.) The reason I'm giving the context is that a lot of people are not really aware of the situation or the risks, and will read a "no thanks" as a polite way to reject. I don't want to set off the usual social scripts and expectations people have for how you are supposed to give a "no thanks," but also I am wary of the social norms that tell people to respect someone's "no thanks." Sometimes I'm not in a position to say no. But I think I've never wanted to say no, and people rarely push, so that's been a good strategy for me.