It's been years since I flew TG long-haul and where I felt like I wanted something between meals, and recall the sandwiches were available. They looked though like the same sandwiches that are available in their lounges (ex-BKK flights), so perhaps easier to just grab a handful of sandwiches in the lounge (if you have access) and then you won't have to worry about whether they're available on the flight, and which variety. Do the sandwiches in the lounge still come tightly wrapped in plastic wrap like they did before? I haven't even bothered to check as I'm no longer the least bit interested in sandwiches.
For me personally, after becoming a picky eater and wanting only items I consider healthy and in-line with my eating/health goals, I simply buy in advance any snacks I think I might need on the flight and bring them with me. That way I'm never disappointed, and the snacks I buy, relative to the cost of the flight, is so tiny that it's of absolutely no consequence. I used to be a bit silly and try to get as much for free as I could, whereas now I try to think about it more logically and choose the way that best suits me and my lifestyle and not worry about the small cost of something.