I use 1mm Silk macrame strings i got from etsy. Pretty sure the exact strings sweets sold/sells as sweets premium but ~25 times cheaper!
Okay I'm hopping on my soap box because I want to immortalize this rant in this thread for anyone reading it in the future. If you're a player who is perusing here to learn about other string options because you want to expand your horizons and try some strings that perform in unique or specific ways, have at it. If you're here to try and save money by finding the same string that a certain company sells but at a lower cost, get outta here and buy a damn string pack! String packs are one of the cheapest ways we can support the companies who keep dama alive and allow us to keep enjoying this game and this community. Kendama companies have done a ton of work to find the strings that will give you the best overall performance, and for the most part offer them at a super low cost. Delving into the world of ordering alternative strings is fun, but not always something that will help progress your play (if that's what you're into). For example: Lovely knots, which is largely considered to be the most popular alternative string option, is amazing only for jug lines. If you are a beginner player or someone who is not interested in doing jug lines, Lovely Knots is not a good option for you. It will likely limit your play and make other kinds of tricks significantly harder. I'm not about hacking the system or undercutting anyone. I've posted a lot of links to random strings in this thread, and the last thing I want is to dissuade anybody from buying a string pack who would otherwise be perfectly happy with one. Suffice it to say: The best all purpose kendama strings money can buy are the ones you can purchase from a kendama company. If you need something specific that isn't already offered, some of the links here are good places to start.