3.5" NH (NST) Male Hose Lightweight Aluminum Fire Plug FM1010 but you could also use

but you could also use some standard drinking jugs when you're on the go

Industrial & Fire 5” Storz x 5” NH (NST) Female Long Handle Swivel Fitting Anodized Aluminum

This will reduce your 3" outlet or hose down from 3" NST Female to 1

Industrial & Fire 6” NH (NST) Female Long Handle Swivel x 6” NPT Male Rigid Fitting Anodized Aluminum

5" NPT Male Threads

3.5" NH (NST) Male Hose Lightweight Aluminum Fire Plug FM1010 but you could also useSpecifications Male Side 3. 5 NH (NST) Male (National Hose National Standard Thread ) Working Pressure 300PSI Max Test Pressure 1000PSI Max Material T 6061 Aluminum (Aircraft Grade) Finishing Anodized (99. 9% Lead Free) NFPA Standards 1963, 4. 12, 5. 1 5. 6. 4 (Corrosion Resistance) Military Standards MIL A 8625 Type III, Class 1 Industrial Standards International ASTM B221 UL Labs Standards 236 8. 1 Through 8. 2 USDA Standards 5100 190C Tables 1 4