I thought the OP meant they knew benzos with methadone were dangerous and so they were not going to try that but they were wondering if there was something safer which was used to potentiate methadone? For example a lot of people use grapefruit juice (it hasn't worked for me but some people swear by it). Personally if you are just a recreational user of methadone and don't have a high opioid tolerance I wouldn't advise potentiating it with anything, but potentiators can be helpful for someone who is, for example, using methadone to help with opioid withdrawal and only has a small quantity of methadone which isn't really enough on its own. The problem is you don't know in advance how much a specific substance/food/drink will potentiate the methadone so it could cause you to overdose.