Let’s go through this step-by-step.

**1. Industry and business profile**  
Veolia is in environmental services (water, waste, energy), which is a mix of regulated and unregulated activities with long-term contracts and concessions. The business risk profile tends to be fairly stable, but the 2022 acquisition of Suez significantly increased Veolia’s scale, debt, and integration complexity.

**2. Current hybrid position**  
- "Titres Super Subordonnés à Durée Indéterminée" (deeply subordinated/hybrid securities) at end-2022: €3,496m.  
- Equity at end-2022: €14,867m.  
- Total adjusted capital is not given directly, but even using a rough proxy of equity + hybrid, hybrids are already a significant share. If total adjusted capital ≈ €14,867m + adjusted debt (likely much larger), the current hybrid % is probably already close to or above 7.5%, potentially limiting further issuance.

**3. Credit metrics and leverage**  
- S&P Net Debt/EBITDA 2022: 3.92×.  
- FFO/Net Debt: 19.72% — this is typical for BBB/BBB+ range utilities/infrastructure, but with limited headroom.  
- Moody’s leverage trend: deteriorating, pointing to increased debt post-Suez acquisition and integration costs.

**4. Market conditions and cost of hybrid**  
- EUR swap rates and IG bond yields have risen sharply in 2022 (5Y swap average: 1.73% vs negative in 2020–2021).  
- The sub-senior spread delta over iBoxx IG in 2022 was ~2.30%, making new hybrid issuance notably more expensive than in prior years.  
- For Veolia, new hybrid coupons would likely materially exceed the average cost of existing debt, moving it toward or beyond “cost of hybrid will materially increase current cost of debt” territory.

**5. Guidance mapping**  
Given the elevated current hybrid amount, deteriorating leverage trend, and higher refinancing costs:
- Current hybrid stock is already high relative to equity.  
- The need for further rating support exists but further issuance would have a diminishing benefit and higher cost.  
- Moderate refinancing/integration needs argue against 0%, but the cost and existing level argue against going to 11.25% or 15%.  
- A modest top-up (in the 3.75% range) could be used for limited flexibility without a significant cost penalty.  

However, given Veolia already has a large outstanding hybrid amount, any new issuance would push it well above the 7.5% range in total adjusted capital, but the guidance says previous issuance is a strong indicator—yet here, it also implies they may already be near their practical limit under S&P’s 15% cap if adjusted debt is large. The more prudent advice would be to limit additional hybrid issuance so as not to push too close to the 15% cap, and given the high cost environment, **3.75%** is the most justifiable moderate option.

<answer>3.75%</answer>