I know this post is from last year lol (not in a old way), so sorry for the lateish repy. Anyways, you can try Tonic Water as another option to grapefruit juice.
Thats what I have done in the past (for Oxy, so it maybe a lil different for hydro), and has worked wonders. I used to drink 8-12 ounces 30-45 mins prior to dosing. It definately lengthened and pontentiated the original dose quite considerably, atleast for me it did. Tonic water contains Quinine which blocks CYP2D6 and induces CYP3A4. So the result is less Norhydrocone & Norhydromorphone and Increased amounts of Hydromorphone.
Tonic water is pretty cheap too if you get the store brand. Though I will warn you right off the bat that it does have bitter taste to it because of Quinine. Its not unbearable, though it may be an acquired taste for some over time. Also tonic water does have a bit sugar added to it, though not as bad soda pop, keep that in mind if you diabetes or blood sugar problem at hand. I WOULD NOT Suggest diet Tonic Water as substitute. It taste horrible and makes it that much unbearable to drink, so do even bother lol.
If your really into pontentiating with tonic water, and want to be more economical about it, you can always just buy Cinchona Bark powder which has quinine and dozens of others alkaloids related to quinine. Then put the powder into capsules with a capsule making machine (There is alot more to it than what I said, I just kept it short and simplified. One would atleast need a scale in the 1000ths of a milligram scale out doses when finding proper dose and so on). That way you can consume it without having to worry about ingesting ounces of fluid, and you will get health benifits from the tree bark with all alkoloids in it.
I would to like lay down a Stern DISCLAIMER with making your own capsules of quinine, unless your willing have dedication, patience, intune with yourself and how you feel, i would NOT Recommend this for most people because if calculated wrong you can OD and possibly DIE from it. But if done right its a game changer along with health benifits.
Hope That Helps OP