What worked for me (diagnosed with ADHD) is to stream my desktop to a friend and have 1.5h work periods with 1h pause inbetween.
Being watched by someone who knows you're supposed to be doing one thing and one thing only can be a great help in refocusing even if one strays a little.
Being watched by someone who knows you're supposed to be doing one thing and one thing only can be a great help in refocusing even if one strays a little.