Do you mean APUs as “auxiliary power units” (aircraft/trucks) or “APU” as AMD’s accelerated-processing units (CPUs with integrated graphics)? I’ll cover the top brands in the three common meanings:

1. Aircraft APUs (airliner / business-jet / military APUs)

• Honeywell Aerospace — market leader with a very large installed base (131, 331 families, HGT series). (aerospace.honeywell.com)
• Pratt & Whitney (Pratt & Whitney Canada) — major competitor, supplier of APUs for some widebodies and regional platforms. (prattwhitney.com)
• Safran Power Units / Safran group — produces APUs and power units for business jets, helicopters and regional aircraft. (en.wikipedia.org)
• Collins Aerospace / Hamilton Sundstrand (historic APS3200 lineage) — long-time supplier / legacy product lines. (prnewswire.com)

2. Truck / heavy-vehicle APUs and idle‑reduction units (cab comfort, hotel loads)

• Thermo King (TriPac / TriPac Envidia) — widely used TriPac diesel and electric APUs; strong dealer/service network. (thermoking.com)
• Carrier Transicold (ComfortPro, Aspen) — ComfortPro (electric / Li‑ion) and Aspen diesel APUs for sleeper cabs. (carrier.com)
• Cummins / Onan (ComfortGuard, Onan gensets) — Cummins offers integrated APU/generator solutions and Onan product heritage. (fleetowner.com, ccjdigital.com)
• Other niche suppliers: GoGreen, TruckGen and various genset/APU specialists — useful for specific budgets or retrofit markets. (gogreenapu.com, fleetowner.com)

3. “APU” in consumer/PC context = AMD Accelerated Processing Units (CPUs with integrated Radeon graphics)

• AMD (Ryzen / Ryzen G / Ryzen 8000G etc.) — the company that produces modern APUs (Ryzen with Radeon integrated graphics; recent Ryzen 8000G/7000G/6000G mobile/desktop APU families). AMD is the dominant vendor for x86 APUs. (en.wikipedia.org, techpowerup.com)

If you meant a different “Apu” or want a ranked “top N” list for one of those categories (e.g., best truck APUs for fuel savings, best AMD APUs for gaming, or market-share leaders in aircraft APUs), tell me which category and I’ll give a short ranked recommendation with prices/spec highlights and sources.