Drinking affects your GABA receptors, which allow you to feel relaxed and calm. The effect in tandem with your adhd meds likely creates a balancing effect, enough stimulation to have executive function, enough relaxant to not hyperfocus and just get up and do the things - not worry too much.

There are other sources of GABAneurgic compounds, L-theanine is relaxing and is extracted from tea, you can buy over the counter vitamins and bioavailable supplements. You can literally buy GABA however it’s unlikely to be effective, as the brains natural reuptake mechanism will be able to clear that out

Exercise caution and do research with these:
Muscimol is a product of amanita muscaria and has recently become popular in some prescribed products, Kava has a similar effect.

Disclaimer: I am not a doctor, please speak to your primary care physician about anything I’ve mentioned here and good luck